Daddylonglegs
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| posted on 20/1/12 at 01:42 PM |
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O/T - Electrical Question
Hi all,
Recently moved into a new place and I am having issues with the garage electrics.
All was fine for a few weeks but a few days ago, the RCD tripped. I reset it but it tripped straight away. There is one main and one each for the
lights and sockets.
If I leave the light one off and the socket one on all is fine. But sometimes (and this is the annoying bit - not always) if I switch the lighting
breaker back on it trips the main RCD, whether the lights are on or not. It will work OK sometimes but then trips some time later, normally at night
of course!  . I have had a look inside and all the connections seem fine and there are no issues I can see with the lighting circuits, but
obviously something is amiss. I have reset it and watched it trip after a minute or so without touching anything?
It might be my imagination, but it seems to have started after we had several days of really cold weather followed by a sudden rise in temperature,
and consequently there was a lot of condensation in the garage, including the light switches. I thought that maybe it would improve after a couple of
days assuming it was condensation causing the trip, but not so.
Any ideas out there please?
Thanks.
John
It looks like the Midget is winning at the moment......
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blakep82
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| posted on 20/1/12 at 01:50 PM |
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i assume the RCD switches are sprung to go off, maybe whatever holds it 'on' is weak? new RCD perhaps? if everything else is fine, no
shorts etc?
________________________
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tegwin
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| posted on 20/1/12 at 01:52 PM |
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I suspect the damp has highlighted an issue and you are getting earth leakage!
I would check resistances on the L,N And E in the garage and see if anything is amiss... It is either a slightly worn cable, or a dodgy connection
somewhere... even a screw terminal not quite tight enough can cause issues,
------------------------------------------------------------------------------------------------------------------------
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MikeRJ
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| posted on 20/1/12 at 01:59 PM |
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You have an earth leakage. Since it has coincided with wet weather, check any outside lighting (lamp fittings and switches).
[Edited on 20/1/12 by MikeRJ]
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ernie
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| posted on 20/1/12 at 02:45 PM |
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Also check all PVC wiring withing garage and if any external wiring for damage by squirrels/mice/rats
PANDE FIRE & SECURITY SYSTEMS
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big-vee-twin
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| posted on 20/1/12 at 05:29 PM |
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Do you have fluorescent lighting, you may find the control gear inside is leaking to earth causing you your problem, you will not be able to see
anything wrong.
Could disconnect each in turn then power up to see which one is faulty.
Duratec Engine is fitted, MS2 Extra V3 is assembled and tested, engine running, car now built. IVA passed 26/02/2016
http://www.triangleltd.com
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Daddylonglegs
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| posted on 20/1/12 at 05:50 PM |
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Thanks for all the input guys 
Problem is, it's nothing to do with using the lights, I can leave everything switched off and if I switch only the socket breaker on, the main
RCD never trips, but if I put the light breaker on sometimes it trips the main one straight away, other times it can take several minutes, but it
eventually will trip it. I can have all the lighting on when I reset it and it makes no difference to when it trips.
The layout is:
Main RCD switch 1 x 40A, 1 x 6A trip for lights, 1 x 20A
2 x double sockets
1 x bayonet light fitting
2 x flourescent strip lights
It looks like the Midget is winning at the moment......
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phoenix70
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| posted on 20/1/12 at 06:45 PM |
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I would check all the terminal in the light switches and fitting are nice and tight.
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JoelP
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| posted on 20/1/12 at 06:53 PM |
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It must be a slight short between live and earth on the lighting circuit but before any switches. Cant be to neutral because having the mcb off
wouldnt affect it, and cant be after the light switches because they are off too! Also check the perminant live feed to any PIR lights.
Insulation tester is what you need.
Beware! Bourettes is binfectious.
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Ben_Copeland
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| posted on 20/1/12 at 06:53 PM |
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Just because the lights aren't on doesn't mean it's ruled out, as soon as you switch the breaker on its supplying power to the
cable. If there is a problem with the cable it will trip, light on or off.
[Edited on 20/1/12 by Ben_Copeland]
Ben
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Ninehigh
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| posted on 20/1/12 at 07:16 PM |
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From what I understand it never trips if only the sockets are on. In which case the sockets are the only ones that are fine.
It looks like it's going to be a long process but might well be best to change everything one by one from the rcd onwards
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JoelP
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| posted on 20/1/12 at 07:43 PM |
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If you cant get an insulation tester, why not turn off the circuit, remove all fittings, and bring them inside the house to dry them out. It is almost
certainly damp thats causing this.
Beware! Bourettes is binfectious.
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big-vee-twin
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| posted on 20/1/12 at 07:44 PM |
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Sounds like you have a high resistance fault possibly due to damp as you have already said, take out all the lamps and disconnect the fluorescent
fittings from the wiring, close your light switches and energise the circuit, this will test the wiring if it doesn't trip then its most likely
to be in one of the lights.
Terminate any live ends into a terminal block before you turn on.
This will allow you to test without the use of a meter.
re connect the lights one by one until you find the problem fitting.
Duratec Engine is fitted, MS2 Extra V3 is assembled and tested, engine running, car now built. IVA passed 26/02/2016
http://www.triangleltd.com
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Daddylonglegs
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| posted on 25/1/12 at 07:04 PM |
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Thanks to all for the input 
Top marks to ernie! damn rodents had nibbled away at about 18", just enough to expose some of the copper and most of the inner sleeving
Replaced the length of wire from consumer unit to light and sorted.
I knew there had been rats before (lots of rat cr*p!) butit was quite old, obviously they left a little gift before they moved on.
Thanks again guys 
It looks like the Midget is winning at the moment......
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